1. Field of the Invention
This invention relates to a controlled action, manually operable fluid applicator of the type in which a user, while holding the applicator in one hand, operates a fluid dispensing actuator to drive fluid from a reservoir and out of the applicator, through an applicator tip. Such applicators have many different uses and are particularly well suited for dispensing glues and adhesives and indeed are common household items for applying epoxy glues, viscous carpentry glues and caulks and so on. More specialized uses with greater performance requirements, as will be described herein, are for applying tissue adhesives in a surgical context to repair tissues damage, and for equivalent professional, medical, veterinary or biological uses.
2. Description of Related Art Including Information Disclosed under 37 CFR 1.97 and 37 CFR 1.98
The above described fluid applicators provide better control over the fluid emerging from the applicator than is possible by simply squeezing a deformable tube of glue to expel the glue from a nozzle attached to the tube. Nevertheless, the control achievable with known applicators is insufficiently precise for many applications. In particular, in surgical applications, there is a need for a fluid dispenser to dispense tissue adhesive which can be precisely and predictably controlled by the user to dispense and apply small quantities of adhesive to target locations. Furthermore, there is a need for an applicator that can be held in a number of different ergonomically desirable configurations. There are a number of teachings in the literature of specialized applicator constructions including those of the present inventor, which have been designed to meet the particular needs of tissue adhesive application, but none is wholly satisfactory owing to deficiencies in the drive mechanism which translates manual force applied to the actuator into movement of the fluid out of the applicator.
In an important optional construction, multiple fluids are held in multiple reservoirs may be dispensed with or without mixing within the applicator. Common household epoxy glue applicators dispense parallel streams of resin and hardener for external mixing and teach that mixing within the applicator, or on its external surfaces, should be avoided to prevent bonding and blockage of its fluid passageways. In contrast, a tissue adhesive applicator, such for example as disclosed in Epstein U.S. Pat. Nos. 5,226,877 and 5,405,607 has reservoirs for two fluids, for example a fibrinogen-containing phase and a thrombin-containing phase, a mixing chamber and a single outlet port for the mixed fluids.
In the described applicators, manual effort provides the necessary drive force and typically, but not necessarily, the applicator has a barrel which can be comfortably held while leaving the thumb free to operate the dispensing actuator which is conveniently positioned for the purpose. An extended applicator tip, which may have a variety of conformations, enables skilled users to apply the dispensed fluid to a target location with considerable precision. Preferably, the applicator is neutral to handedness, being equally amenable to left-hand or right-hand operation. A well known fluid applicator construction comprises a barrel-like body intended to be gripped in the user's hand, which body incorporates a fluid reservoir, and a trigger-like, spring-return fluid-dispensing actuator, manually applied pressure on which drives fluid out of the reservoir through an applicator tip. The drive mechanism comprises a toothed rack extending the length of the reservoir to be discharged, a plunger and a drive pawl, the plunger and drive pawl being coupled with the trigger actuator via pivot means so that operation of the actuator causes the drive pawl to engage the rack teeth, to pivot and index the plunger into the reservoir. On the return path, the drive pawl rides back over the rack while engagement of a second, locking pawl with the toothed rack prevents drawback. Such applicators are commonly available in hardware stores and are standard issue for dispensing and applying caulking, construction adhesive and the like. Generally, they provide an increasing mechanical advantage as the trigger is squeezed, making steady controlled application of fluid difficult to achieve. For this and other reasons, such hardware store applicators are not suited to medical and surgical uses.
Laghi, U.S. Pat. No. 5,328,459, addresses the need for generating high pressures to produce low flow rates when dispensing thixotropic or non-Newtonian fluids. Laghi employs small electric motors, preferably stepper motors, for providing high torque when driving a dispenser which expensive and cumbersome remedy does not solve the problems faced by surgeons wishing to apply one or more medically useful fluids to patients during surgery.
Rowe et al., U.S. Pat. No. 5,612,050, discloses an applicator which employs a trigger-actuated compression spring to provide a driving force for dispensing polymeric fluids to a site on the tissue of a patient. The trigger 182 includes a cam surface 180 which increases the mechanical advantage on a compression link 158 as the squeezing of the trigger progresses providing the user with an unbalanced response, making it difficult adequately to control the discharge of fluid.
There is accordingly a need for a manually operable fluid applicator that has a controlled action suiting it to precision applications such, for example, as dispensing and applying medically useful fluids during surgery.